1. Field of the Invention
The present invention relates to a resin having excellent heat resistance and mechanical properties, a thermosetting composition affording said resin and a prepolymer obtained by pre-reacting said composition.
2. Description of the Prior Art
As resinous molding materials having a thermal resistance of class H, addition-polymerization type polyimides such as bismaleimide have been well known. Bismaleimide is used in combination with a diamine or both diamine and epoxy resin in many cases. The specification of British Pat. No. 1,322,332 discloses aromatic dicyanamide homopolymers but they cannot be used as molding materials or starting materials for films, coating agents or prepreg materials, since they have only a poor flexibility, though their heat resistance is superior to that of the polyimide.